I ordered the base 27 with a 3tb Fusion drive now after reading on this forum I'm wondering if I should change my order to a 1tb Fusion drive and go with a faster processor and graphics? Does anyone have any advice? This is my first iMac so I want to get it right. Thanks!

More seriously, nobody can answer without more info.
- If you are a gamer, go for faster processor and graphics
- If you do video editing, it depends, but probably processor and graphics
- Otherwise, processor and graphics won't bring you a significant difference
- There's one aspect of a larger hard drive nobody talks about. It's not just a question of space you need. If you're using 800Mb on a 1TB hard drive, your system will be slightly slower than using 800Mb on a 3TB system. Since the hard drive is probably the bottleneck of this kind of system, you want to improve its performance as much as you can, i.e. SSD>Fusion>Larger Hard drive>smaller hard drive

I ordered the base 27 with a 3tb Fusion drive now after reading on this forum I'm wondering if I should change my order to a 1tb Fusion drive and go with a faster processor and graphics? Does anyone have any advice? This is my first iMac so I want to get it right. Thanks!

In order to get the faster processor and graphics, you would need to step up to the high end 27